using System;

public class Program

{

    public static void Main(string[] args)

        {

            int sum = 0;

            string input;

​

            do

            {

                Console.WriteLine("\nEnter a number or 'ok' to quit");

                input = Console.ReadLine();

​

                if (input != "ok")

                {

                    int number = int.Parse(input);

                    sum = sum + number;

                }

            } while (input != "ok");

​

            return;

        }

}